I think the system needs to have a field with unique value to make sure we do not upload duplicated items on our site. With the number of items increases, it would be very hard for us to memorize and check if the item has already been uploaded or not. Two many duplicated items will make the site look bad.

We need to have such a field for each item. So if we accidentially upload the same item, the program can pop-up an error message "Sorry. The same item has already been added [link to that item]."

Please don't make Model required to be unique. Some of us that don't have products with UIDs use that field for other things (since it's required to be filled in) and we don't want to have to add random numbers to the end of the field to enter a product.

If you do decide to use Model for the UID, at least make it only give a warning instead of making it a requirement.